JP2011043154A - Control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve controllability and exhaust in a transition zone by preventing increase of the absolute value of a switching function vector calculated based on a state variable in control of an internal combustion engine or a device accompanying the same by utilizing a sliding mode controller for repetitively calculating linear input and non-linear input with reference to the state variable as the time integral of the deviation of a control output and its target value. <P>SOLUTION: A control device (ECU) for controlling the internal combustion engine or the device accompanying the same includes a sliding mode controller, and a correction control part for stopping updating of the state variable when a condition of having the absolute value of the change amount of a control output corresponding to the change amount of the non-linear input lower than a predetermined threshold value satisfied with the premise that a switching function vector calculated based on a state variable is changed by a predetermined change amount, and resuming updating of the state variable when the deviation of the control output and its target value changes from plus to minus or minus to plus in the period with updating of the state variable stopped. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a control device for controlling an internal combustion engine or a device attached thereto.

  An exhaust gas recirculation system disclosed in Patent Document 1 below controls an EGR rate (or EGR amount) of an internal combustion engine equipped with a supercharger. There is mutual interference between the supercharging pressure and the EGR rate, and it is difficult to simultaneously control both the supercharging pressure and the EGR rate with a one-input one-output controller. In addition, the responsiveness varies depending on the operation region of the internal combustion engine, and the turbocharger has a turbo lag (dead time). Under such circumstances, the system described in Patent Document 1 employs sliding mode control, which is an effective control method for a non-linear control target, and designs a multi-input multi-output controller that takes into account the interaction. I have control.

When a deviation remains between the measured value of the control output and the target value, the sliding mode controller operates the operation unit to reduce this deviation. Here, the sliding mode controller uses, for example, the time integration of the deviation between the target value of the control output and the actual measurement value as a state variable, and refers to this state variable to the linear input U _eq and the nonlinear input as elements of the control input U. U _nl is iteratively calculated.

In general, a smoothing coefficient for preventing the occurrence of chattering is introduced into the formula for calculating the nonlinear input _Unl . At this time, the nonlinear input U _nl is a function of the switching function vector σ, and when the absolute value of each component of the switching function vector σ increases, the nonlinear input term U _{nl with} respect to the amount of change of each component of the switching function vector σ. The amount of change tends to be small.

When the deviation between the target value of the control output and the actual measurement value remains, the absolute value of the time integration of the deviation increases and σ = SX _e (S is a matrix constituting the switching hyperplane, and X _e is the state quantity vector. ), The absolute value of each component of the switching function vector σ continues to increase. On the other hand, since the change amount of the control input becomes small, the change amount of the control output also becomes small, and the deviation of the control output remains without converging.

For this reason, the absolute value of each component of the switching function vector σ continues to increase further and may take an extreme value. Thereafter, even if the polarity of the deviation of the control output is reversed, as described above, the change amount of the nonlinear input term _{Unl with} respect to the change amount of each component of σ is small, and therefore it takes time to reach the target value of the control output. . As a result, problems such as controllability in the transition region and exhaust gas deterioration occur.

JP 2007-032462 A

  The present invention, which has been made paying attention to the above, is intended to prevent the occurrence of problems that occur when the absolute value of the state variable continues to increase.

  A control device according to the present invention controls an internal combustion engine or a device attached thereto, and uses a time integral of a deviation between a control output and its target value as a state variable, and refers to the state variable for linear input and A sliding mode controller that repeatedly calculates a nonlinear input, and a control output corresponding to the amount of change in the nonlinear input that occurs when it is assumed that the switching function vector calculated based on the state variable has changed by a predetermined amount of change. When the condition that the absolute value of the change amount falls below a predetermined threshold is satisfied, the update of the state variable is stopped, and the sign of the deviation between the control output and the target value during the period when the update of the state variable is stopped And a correction control unit that restarts the update of the state variable when the value changes.

  In the present invention, when the condition that the absolute value of the change amount of the control output corresponding to the change amount of the nonlinear input generated when it is assumed that the switching function vector has changed by a predetermined change amount falls below a predetermined threshold value is satisfied. In other words, when reaching a region where a change in a predetermined amount of the switching function vector has a negligible influence on the control output, by stopping the update of the state variable, each component of the switching function vector is stopped. Suppresses the increase in absolute value. In addition, when the sign of the deviation between the control output and its target value changes during the period when the update of the state variable is stopped, the sign of the deviation changes in the nonlinear input by resuming the update of the state variable. Can be quickly changed in the opposite direction. Therefore, controllability in the transition region and exhaust gas can be improved.

  Further, while controlling a plurality of control outputs, the state variables and thresholds are set for each control output, and if the state variables are stopped and restarted for each state variable, Even if updating of one state variable is stopped, updating of other state variables can continue. That is, it is possible to prevent the adverse effect on the control of the control output corresponding to the other state variables by stopping the update of one state variable.

  On the other hand, the internal combustion engine or the device attached thereto is controlled by operating a plurality of operation units, and the amount of change in the control output corresponding to the amount of change in the nonlinear input to be compared with the threshold is determined for each operation unit. Of the change amount of the control output corresponding to the change amount of the non-linear input that occurs when it is assumed that the switching function vector calculated based on the state variable has changed by a predetermined change amount. If the condition that the amount of change in the component corresponding to any one of the operation units falls below a predetermined threshold is satisfied, if the state variable update is stopped, the condition for stopping the state variable update is operated. It can be set for each part, and the increase can be prevented before the absolute value of each component of the switching function vector takes an extreme value. “The amount of change in the control output corresponding to the amount of change in the nonlinear input to be compared with the threshold value is set for each operation unit” means that the component corresponds to each component of the switching function vector. This is a concept including setting the change amount of the control output for each term. In addition, “the condition that the amount of change in the component corresponding to any one operation unit is lower than a predetermined threshold” means that when the component is indicated by the sum of terms corresponding to each component of the switching function vector, This is a concept including the condition that the term is below a predetermined threshold.

  In the control device according to the present invention, the condition that the absolute value of the change amount of the control output corresponding to the change amount of the nonlinear input that occurs when it is assumed that the switching function vector has changed by a predetermined change amount is below a predetermined threshold value. In other words, by stopping the update of the state variable when reaching a region where the influence of the change of the predetermined amount of the switching function vector on the control output is negligible, the switching function vector Suppresses the increase in absolute value of each component. In addition, when the sign of the deviation between the control output and its target value changes during the period when the update of the state variable is stopped, the sign of the deviation changes in the nonlinear input by resuming the update of the state variable. Can be quickly changed in the opposite direction. Therefore, controllability in the transition region and exhaust gas can be improved.

The hardware resource block diagram of the EGR system in one Embodiment of this invention. Configuration explanatory drawing of the control apparatus of the embodiment. The block diagram of the sliding mode controller of the embodiment. The figure which illustrates the relationship between a switching function and a nonlinear output. The figure which illustrates the map which defined the relationship between each control input and each control output. The figure which illustrates the map which defined the relationship between the nozzle opening degree of a variable turbo, and an EGR rate. The flowchart which shows the flow of a process of the program which the control apparatus of the embodiment performs.

  An embodiment of the present invention will be described with reference to the drawings. What is shown in FIG. 1 is an EGR system that is one of the objects to which the present invention is applied. This EGR system attached to the internal combustion engine 2 includes measuring devices (or sensors) 11 and 12 for detecting values related to a plurality of fluid pressures or flow rates in the intake and exhaust systems 3 and 4, and target values for these values. An ECU (Electronic Control Unit) 5 serving as a control device that operates the plurality of operation units 45, 42, and 33 to set each value and follow the target value is provided.

  The internal combustion engine 2 is a diesel engine equipped with a supercharger, for example. The intake system 3 of the internal combustion engine 2 is provided with a variable turbo compressor 31 and an intercooler 32 for intake air cooling and a D throttle valve 33 for adjusting the intake air (fresh air) amount downstream thereof. Further, a flow meter 11 for measuring the intake air amount and a pressure meter 12 for measuring the intake pipe pressure are installed.

  A turbine 41 for driving the compressor 31 is disposed in the exhaust system 4 of the internal combustion engine 2, and a variable turbo nozzle 42 for increasing / decreasing the A / R ratio of the supercharger is provided at the inlet of the turbine 41. A DPF (Diesel Particulate Filter) (not shown) is installed downstream of the turbine 41. Then, an EGR passage 43 for recirculating a part of the exhaust gas discharged from the combustion chamber of the internal combustion engine 2 to the intake system 3 is formed. The EGR passage 43 is connected downstream of the D throttle valve 33 in the intake system 3. The EGR passage 43 is provided with an EGR cooler 44 for cooling the exhaust, and an external EGR valve 45 that adjusts the amount of EGR gas that passes therethrough.

  In the present embodiment, a target value is set for each of the EGR rate (or EGR amount) and the intake pipe pressure, and a plurality of operation units, that is, an EGR valve 45, Control for operating the variable turbo nozzle 42 and the D throttle valve 33 is performed.

  The EGR valve 45, the variable turbo nozzle 42, and the D throttle valve 33 are controlled by the ECU 5 to change the opening thereof linearly. Each operation unit 45, 42, 33 is combined with an electric valve that changes the opening by increasing or decreasing the duty ratio of the drive signal, or a vacuum control valve, etc. It uses mechanical valves that change.

  The ECU 5 is a microcomputer including a processor, a RAM (Random Access Memory), a ROM (Read Only Memory) or a flash memory, an A / D conversion circuit, a D / A conversion circuit, and the like. In addition to the measuring instruments 11 and 12 for detecting the EGR rate and the pressure in the intake pipe, the ECU 5 detects various measuring instruments for detecting the engine speed, the amount of depression of the accelerator pedal, the cooling water temperature, the intake air temperature, the outside air temperature, etc. (Not shown) can be electrically connected to each other to receive signals output from these measuring instruments to obtain each value.

  Incidentally, in this embodiment, the EGR rate is not directly measured. The amount of air entering the cylinder of the internal combustion engine 2 can be predicted based on the opening of the variable turbo nozzle 42. When the predicted value of the air amount is set as gcyl and the intake air amount measured by the flow meter 11 is set as ga, the relationship of eegr = 1−ga / gcyl is established for the estimated EGR rate eegr. The ROM or flash memory of the ECU 5 stores in advance map data that defines the relationship between the opening degree of the variable turbo nozzle 42 and the amount of air entering the cylinder. The ECU 5 searches the map using the opening of the variable turbo nozzle 42 as a key, obtains a predicted value of the amount of air entering the cylinder, and substitutes this and the intake air amount into the above equation to calculate the EGR rate.

  In addition, the ECU 5 is electrically connected to an EGR valve 45, a variable turbo nozzle 42, a D throttle valve 33, an injector that controls fuel injection, a fuel pump, and the like (not shown). A signal can be input.

  A program to be executed by the ECU 5 is stored in advance in a ROM or a flash memory, and is read into the RAM at the time of execution and is decoded by the processor. The ECU 5 controls the internal combustion engine 2 according to a program. For example, the required fuel injection amount (in other words, engine load) is determined based on various conditions such as engine speed, accelerator pedal depression amount, and coolant temperature, and a drive signal corresponding to the required injection amount is input to an injector or the like. And control the fuel injection. In addition, the ECU 5 exhibits functions as the servo controller 51 and the correction control unit 52 shown in FIGS. 2 and 3 according to the program.

  The servo controller 51 is a sliding mode controller and is responsible for the sliding mode control of the EGR rate and the intake pipe pressure. During feedback control, the ECU 5 receives signals output from various measuring instruments (not shown), and knows the engine speed, accelerator depression amount, cooling water temperature, intake air temperature, external temperature and pressure, etc., and the required injection amount To decide. Subsequently, the target EGR rate and the target intake pipe pressure are set based on at least the engine speed and the required injection amount. The ROM or flash memory of the ECU 5 stores in advance map data indicating each target value to be set according to the engine speed and the required injection amount. The ECU 5 searches the map using the engine speed and the required injection amount as keys, and obtains target values for the EGR rate and the intake pipe pressure. Further, the target value obtained by referring to the map is set as a basic value, and this is corrected according to the cooling water temperature, the intake air temperature, the outside air temperature, the atmospheric pressure, and the like to obtain the final target value.

  Then, the ECU 5 receives signals output from the measuring instruments 11 and 12 to obtain the current values of the EGR rate and the intake pipe pressure, and the opening of the EGR valve 45 from the deviation between the current value of each control variable and the target value. Then, the opening of the variable turbo nozzle 42 and the opening of the D throttle valve 33 are calculated, and a drive signal corresponding to each operation amount is input to the operation units 45, 42, 33 to operate the opening.

  A supplementary explanation will be given regarding adaptive sliding mode control of the EGR rate. The state equation and the output equation are as shown in the following equation (Equation 1).

  In this embodiment, the state quantity vector X has a structure that can be directly obtained from the output vector Y. In other words, a value that can be detected via the measuring instruments 11 and 12 is directly controlled, so that the state estimation observer. This prevents the deterioration of the control performance due to the estimation error. The output matrix C is known, and is a unit matrix in this embodiment.

  In plant modeling, that is, identification of the coefficient matrix A and the input matrix B in the state equation (Equation 1), the opening degree is manipulated by inputting M-sequence signals having various frequencies to the operation units 45, 42, and 33. Then, the values of the EGR rate and the intake pipe pressure are observed, and the matrices A and B are identified from the input / output data. It is assumed that the M-sequence signals input to the operation units 45, 42, and 33 are uncorrelated with each other. This makes it possible to create a model that takes into account the mutual interference between the values.

FIG. 3 shows a block diagram of the adaptive sliding mode control system of the present embodiment. The design procedure of the sliding mode controller 51 includes the design of the switching hyperplane and the design of a nonlinear switching input for constraining the state quantity to the switching hyperplane. If a new state quantity vector _Xe is defined by adding an integral value vector Z of the deviation between the target value vector R and the output vector Y to the original state quantity vector X in order to constitute a type 1 servo system, The equation of state of the expanded system shown in (Expression 2) is obtained.

  In consideration of the stability margin, the design method using the zero of the system is used to design the switching hyperplane. That is, the hyperplane is designed so that the equivalent control system is stable when the expansion system of the above equation (Equation 2) is generating the sliding mode. When the switching function σ is defined by Expression (Expression 3), σ = 0 and Expression (Expression 4) holds when the state is constrained to the hyperplane.

  Therefore, the linear input (equivalent control input) when the sliding mode occurs is expressed by the following equation (Equation 5).

  Substituting the linear input of the above equation (Equation 5) into the state equation (Equation 2) of the expanded system results in an equivalent control system of the following equation (Equation 6).

  Since designing a hyperplane so that this equivalent control system is stable is equivalent to designing a system ignoring the target value R, the following equation (Equation 7) holds.

  Taking the stability ε into consideration for the system of the above equation (Equation 7), obtaining the feedback gain using the optimal control theory, and making it a hyperplane, the following equation (Equation 8) is obtained.

The matrix P _s is a positive definite solution of the Riccati equation (Equation 9).

Q _s in the Riccati equation (Equation 9) is a weight matrix for control purposes, and is a non-negative definite symmetric matrix. q ₁ and q ₂ are weights for the integral Z of the deviation, and are determined by the difference in the speed of the frequency response of the control system. q ₃ and q ₄ are weights for the output Y, and are determined by the difference in the magnitude of the gain. Further, R _s in the Riccati equation (Equation 9) is a weight matrix of the control input and is a positive definite symmetric matrix. ε is a stability margin coefficient and is specified so that ε ≧ 0.

  Instead of the above equations (Equation 8) and (Equation 9), the following discrete hyperplane construction equation (Equation 10) and algebraic Riccati equation (Equation 11) may be used.

The final sliding mode method is used to design the input for constraining to the hyperplane. Here, the control input U is expressed by the following expression (Equation 12) as the sum of the linear input U _eq and a new input, that is, a nonlinear input (nonlinear control input) U _nl .

  Since it is desired to stabilize the switching function σ, the Lyapunov function for σ is selected as shown in the following equation (Equation 13) and differentiated to obtain the equation (Equation 14).

  Substituting the equation (Equation 12) into the equation (Equation 14) yields the following equation (Equation 15).

When the nonlinear input U _nl to the following expression (Expression 16), the derivative of the Lyapunov function becomes equation (17).

  Therefore, if the switching gain k is positive, the differential value of the Lyapunov function can be negative, and the stability of the sliding mode is guaranteed. The control input U at this time is expressed by the following equation (Equation 18).

  η is a smoothing coefficient introduced to reduce chattering, and η> 0.

  In the sliding mode control, it is necessary to increase the nonlinear gain in order to constrain the state quantity to the hyperplane. However, if the nonlinear gain is increased, chattering occurs in the control input. Therefore, the uncertainty of the model is divided into a definite part whose structure is unknown and whose parameter is unknown, and an uncertain part whose structure is unknown but whose upper bound is known. Uncertainty (f + Δf) is added to the state equation (Equation 1), and is expressed by the following equation (Equation 19).

  The uncertainty determination part f is compensated by identifying the unknown parameter θ. In this case, the switching gain is applied only to the uncertain part Δf of the uncertainty, and the chattering of the control input can be greatly reduced as compared with the case where the switching gain is applied to the entire uncertain component (f + Δf).

The control input U is represented by the following equation (Equation 20) obtained by adding the adaptive term U _ad to the equation (Equation 18).

Γ _{1 at the} control input (Equation 20) is an adaptive gain matrix. The function h is generally a function of the state quantity x and / or the unknown parameter θ. However, in the present embodiment, by making h a simple expression and a constant unrelated to x and θ, x is quickly converged, and θ To increase the adaptation speed. In particular, when h = 1, the estimated parameter can be identified according to the following equation (Equation 21).

In the present embodiment, the EGR ratio y ₁ and the intake pipe pressure y ₂ as a control output variable, the opening degree u ₁ of the EGR valve 45, the opening degree u ₃ of opening u ₂ and D throttle valve 33 of the variable turbo nozzle 42 Performs 3-input 2-output feedback control using as a control input variable. The number of state variables (system order) is 2 in the initial system (Equation 1), and 4 in the expanded system (Equation 2). By specifying the control output and the state quantity in this way, there is no need to install a measuring instrument such as a flow meter at a location where it directly contacts the exhaust gas.

However, in a three-input two-output system as in this embodiment, det (SB _e ) = 0 holds, and the matrix (SB _e ) is not regular. Therefore, the inverse matrix (SB _e ) ⁻¹ is calculated as a generalized inverse matrix. As the generalized inverse matrix, for example, a Moore-Penrose-type inverse matrix (SB _e ) ^† is used.

The control input u ₁ related to the EGR valve 45, the control input u ₂ related to the variable turbo nozzle 42, and the control input u ₃ related to the D throttle valve 33 are respectively a linear input term and a non-linear input as shown in the following equation (Equation 22). It is the sum of the input term and the adaptive term.

Further, from the equation (Equation 12), the equation (Equation 18), and the equation (Equation 20), the nonlinear input _Unl can be expressed by the following equation (Equation 23).

The state quantity vector X _e = [x _e1 x _e2 x _e3 x _e4 ] ^T has, as its components, time integrals x _e1 and x _e2 of deviation between the control output Y and its target value R, and other x _e3 , X _e4 . x _e1 and x _e3 relate to the EGR rate y ₁ as the first control output, x _e2 and x _e4 relate to the intake pipe pressure y ₂ as the second control output, and these state variables x _e1 and x _e3 , x _e2 And x _e4 are individual for each control output y ₁ , y ₂ . Further, x _e3 and x _e4 are respectively connected to the control outputs y ₁ and y ₂ via the output equation (Equation 1). When the time integrals x _e1 and x _e2 of the deviation between the control output Y and the target value R are increased according to (Equation 3) described above, the absolute value of σ increases.

  FIG. 4 schematically illustrates the relationship between the switching function vector σ and JΣ represented by the following equation (Equation 24).

In this embodiment, σ and JΣ are both three-dimensional vectors, so FIG. 4 is not mathematically accurate. However, if it is described with reference to FIG. 4 (or σ and JΣ are both considered as scalar values), JΣ gradually approaches the switching gain k as σ increases. That is, as σ increases, the sensitivity of JΣ to changes in σ decreases as shown in FIG. As a result, the sensitivity of U _{nl to} changes in σ becomes dull. The change in which JΣ approaches the asymptotic line k becomes more rapid as the smoothing coefficient η is smaller and becomes slower as η is smaller.

Therefore, when the condition that the amount of change of the nonlinear input _Unl that occurs when it is assumed that the switching function vector σ has changed by a predetermined change amount Δσ is less than a predetermined threshold is satisfied, The updating of the state variables x _e1 and x _e2 is stopped.

By changing each component σ _j (j = 1 to 3) of the switching function vector σ by a predetermined minimum change amount Δσ _j and setting the amount of change of each component JΣ _j of JΣ as ΔJΣ _j , σ _j becomes Δσ _j by each component of the nonlinear input U _nl when changing u _nl1, u _nl2, u variation of _{nl3 ΔU nl1, ΔU nl2, ΔU} nl3 can be respectively expressed by the following equation (equation 25).

Then, the correction control unit 52 calculates the absolute value of the control output change amount Δy _ijk when the input to the operation units 45, 42, and 33 corresponding to the terms k _ij ΔJΣ _j of (Equation 25) is changed. When the value falls below the threshold th _k , updating of the deviation time integrals x _e1 and x _e2 corresponding to the control output is stopped. Here, the change amount [Delta] y _ijk of the control output as the parameter variation k _ij ΔJΣ _j nonlinear input can be calculated based on input-output characteristic model, as shown in FIGS. Note that the subscript k of the control output change amount Δy _ijk and the threshold value th _k indicates the type of the control output, where k = 1 indicates the EGR rate, and k = 2 indicates the intake pipe pressure.

The threshold th _k is set to a predetermined value for each of the EGR rate and the intake pipe pressure. Specifically, the ECU 5 is set to a value corresponding to the smallest digit bit when counting the EGR rate and the intake pipe pressure. That is, when the change in the EGR rate or the intake pipe pressure that occurs when it is assumed that the switching function vector σ has changed by a predetermined change amount Δσ has become so small that the ECU 5 cannot count, the state variable x Stop updating _e1 and _xe2 . and stops updating the x _e1, x _e2 is the most recent x _e1, x _e2, deviation of the EGR rate and the intake pipe pressure at the current time (r ₁ -y _1), is added to (r ₂ -y ₂₎ It means to stop the integration process. As a result, the state variables x _e1 and x _e2 are held at the latest values.

Further, when the positive and negative deviations (r ₁ −y ₁ ) and (r ₂ −y ₂ ) between the control output and the target value change during a period in which updating of the state variables x _e1 and x _e2 is stopped , The updating of the state variables x _e1 and x _e2 , that is, the integration process is resumed.

  The ECU 5 has a built-in program for performing the control as described above. Hereinafter, the control procedure executed by the program will be described with reference to FIG. 7 which is a flowchart. This program is repeatedly executed every time a predetermined time elapses.

First, in step S1, to obtain the components of the state vector X _e. That is, the time integration x _e1 of deviation from the target value of the EGR rate, the time integration x _e2 of deviation from the target value of the intake pipe pressure, the EGR rate x _e3, and the intake pipe pressure x _e4 are acquired.

  In step S2, the switching function vector σ is calculated by the above (Equation 3).

In step S3, it is determined whether or not the update of the state variable x _ek (k = 1 to 2) has already been stopped. If the update of the state variable x _ek has not been stopped, the process proceeds to step S4. On the other hand, when the update of the state variable x _ek is stopped, the process proceeds to step S8.

In step S4, each component k _ij ΔJΣ _i of the change amount of the nonlinear input U _nl generated when it is assumed that the switching function vector σ has changed by a predetermined change amount Δσ is calculated. Correspondence between Δσ and Derutajeishiguma _i is as is shown in FIG.

In step S5, a change amount Δy _ijk of the control output that occurs when it is assumed that the input to each operation unit 45, 42, 33 has changed by k _ij ΔJΣ _i is calculated. Here, the change amount Δy _ijk of the control output is calculated as follows.

A map indicating the input / output characteristics of the plant is stored in advance in the ROM or flash memory of the ECU 5. An overview of the map is illustrated in FIG. The map shows the relationship between the opening of the EGR valve 45 and the EGR rate, the map showing the relationship between the opening of the nozzle vane 42 and the EGR rate, and the relationship between the opening of the throttle valve 33 and the EGR rate. A map representing the relationship between the opening of the EGR valve 45 and the pressure in the intake pipe, a map representing the relationship between the opening of the nozzle vane 42 and the pressure in the intake pipe, and the relationship between the opening of the throttle valve 33 and the pressure in the intake pipe. There are 6 maps showing the relationship. However, the degree of opening u ₂ and opening u ₃ of the D throttle valve of the nozzle vane 42, is greater control input value u _2, u ₃ (right graph) side closure of the valve, the control input value u _2, u ₃ The small side (left side of the graph) means that the valve is open.

Based on these map data, the correction control unit 52 calculates the change amount Δy _ijk of the control output when the nonlinear input U _nl to each operation unit changes by k _ij ΔJΣ _i of the above (Equation 25). As an example, under the assumption that the opening degree of the EGR valve 45 fluctuates only by k _1j ΔJΣ _i , a map showing the relationship between the opening degree of the EGR valve 45 and the EGR rate is referred to as shown in FIG. Te can Chitoku the variation [Delta] y _ij1 of EGR rate corresponding to the amount of change k _1j ΔJΣ _i input. Although not shown, with reference to a map showing the relationship between the opening degree of the EGR valve 45 and the pressure in the intake pipe, the change amount Δy _{ij2 of} the EGR rate corresponding to the input change amount k _1j ΔJΣ _i. Can be known.

Furthermore, a map showing the relationship between the opening degree of the nozzle vane 42 and the EGR rate, a map showing the relationship between the opening degree of the nozzle vane 42 and the intake pipe pressure, and the relationship between the opening degree of the throttle valve 33 and the EGR rate. Similarly, referring to the map and the map representing the relationship between the opening degree of the throttle valve 33 and the intake pipe pressure, the change amount Δy _ijk (i = 1 to 1) of the EGR rate corresponding to the input change amount k _ij ΔJΣ _i . 3, j = 1 to 3 and k = 1 to 2).

In step S6, whether or not the absolute value | Δy _ijk | of the change amount Δy _ijk (i = 1 to 3, j = 1 to 3, k = 1 to 2) of the control output is below the threshold th _k . Determine. If there is a component in which | Δy _ijk | is below the threshold th _k , the process proceeds to step S7. On the other hand, if there is no component for which | Δy _ijk | is less than the threshold th _k , the process proceeds to step S8.

In step S7, updating of the state variable x _ek related to the control output y _{k for} which | Δy _ijk | is less than the threshold th _k is stopped.

In step S8, the state variables x _e1 and x _e2 are updated.

In step S9, a process in a state that stops updating the state variable x _ek (k = 1~2), the control output y _k corresponding to the state variable x _ek and the target value r _k It is determined whether or not the sign of the deviation (r _k −y _k ) has changed. If the deviation (r _k −y _k ) has changed, the process proceeds to step S7. That is, the update of the corresponding state variable x _ek is resumed. If the sign of the deviation (r _k −y _k ) has not changed, the process proceeds to step S8. That is, the stop of updating of the corresponding state variable x _ek is continuously maintained.

In this program, for each of the EGR rate and the intake pipe pressure, it is determined whether or not the update of the state variable x _ek in step S3 is stopped, and the change amount of the output y _k in step S6 | Δy _ijk | Is less than the threshold value th _k and whether or not the sign of the deviation (r _k −y _k ) in step S9 has changed is determined. Then, only the state variable x _ek corresponding to the control output y _k whose | Δy _ijk | is less than th _k is stopped.

As described above, in the present embodiment, the change amount of the control output corresponding to the change amount of the nonlinear input _Unl generated when it is assumed that the switching function vector σ has changed by the predetermined change amount Δσ is a predetermined amount. When the condition that the threshold value is below the threshold th _k is satisfied, that is, when the state variable reaches a region where the influence on the nonlinear input _Unl can be ignored, the update of the state variable is stopped, thereby Suppresses the increase in the absolute value of the component. On top of that, by resuming the updating of the state variables when the positive and negative changes of the deviation of the control output during the period that stops updating the state variable and the target value, the value of the deviation of the non-linear input U _nl It can be quickly changed in the reverse direction before the change in positive and negative. Therefore, controllability in the transition region and exhaust gas can be improved.

The deviation time integrals x _e1 and x _e2 and the threshold th _k are set for each control output, and the updating of the deviation time integrals x _e1 and x _e2 is stopped and restarted for each state variable. Therefore, even if the update of one state variable is stopped, the update of the other state variable can be continued. That is, it is possible to prevent an adverse effect on the control of the control output corresponding to the other state variable by stopping the update of the one state variable.

Further, the change amount Δy _ijk of the control output to be compared with the threshold value th _k is set for each term k _ij ΔJΣ _i of the above-described (Equation 25) and the change amount k _ij ΔJΣ of the nonlinear input. _When the condition that the change amount of any one of the control output change amounts Δy _ijk corresponding to _i falls below a predetermined threshold th _k is satisfied, the deviation time integrals x _e1 and x _e2 are updated. Since it is stopped, the increase can be prevented before the absolute value of each component of the switching function vector σ takes an extreme value.

  The present invention is not limited to the embodiment described above.

  For example, in the above-described embodiment, the threshold value is set for each operation unit, the condition for stopping the update of the state variable is set for each component, and the absolute value of the change amount of any one of the nonlinear inputs is set. The update of the state variable is stopped when the value is lower than the threshold value. For example, the update of the state variable is stopped when the average value of the amount of change of each component of the nonlinear input is lower than the threshold value. It may be.

  Further, the control input variables in the EGR control are not limited to the EGR valve opening, the variable turbo nozzle opening, and the throttle valve opening. The control output variable is not limited to the EGR rate (or EGR amount) and the intake pipe pressure. It is also possible to construct a tertiary system with four inputs and three outputs by adding new input variables and output variables. For example, when a passage that bypasses the supercharger (compressor) is present in the intake system, a valve provided on the passage may be operated. At this time, the pressure or flow rate in the bypass passage can be included in the control output variable, and the opening of the valve on the bypass passage can be included in the control input variable.

  In addition, various changes may be made without departing from the spirit of the present invention.

5 ... ECU (control device)
51 ... Sliding mode controller 52 ... Correction control unit

Claims (3)

Controlling an internal combustion engine or a device attached thereto,
A sliding mode controller that takes a time integration of a deviation between a control output and a target value as a state variable, and repeatedly calculates a linear input and a nonlinear input with reference to the state variable;
A condition that the absolute value of the change amount of the control output corresponding to the change amount of the nonlinear input that occurs when it is assumed that the switching function vector calculated based on the state variable has changed by a predetermined change amount is below a predetermined threshold value. When the condition variable is satisfied, the update of the state variable is stopped, and the update of the state variable is resumed when the sign of the deviation between the control output and the target value changes in the period when the update of the state variable is stopped. And a control unit. While controlling a plurality of control outputs, the state variables and thresholds are set for each control output,
The control device according to claim 1, wherein the state variable is stopped and restarted for each state variable. The internal combustion engine or the device attached thereto is controlled by operating a plurality of operation units, and a control output change amount corresponding to the non-linear input change amount to be compared with the threshold value is set for each operation unit. And what
Corresponds to any one of the operation outputs of the change amount of the control output corresponding to the change amount of the nonlinear input generated when it is assumed that the switching function vector calculated based on the state variable has changed by a predetermined change amount. The control apparatus according to claim 1 or 2, wherein the update of the state variable is stopped when a condition that the amount of change of the component to be performed falls below a predetermined threshold is satisfied.

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